The present disclosure provides systems and methods to measure pulse and blood oxygen saturation in humans using reflectance spectroscopy.
A blood oximeter measures oxygen saturation percentage in human blood by comparing the amount of light absorbed by the blood (which has different molar extinction coefficients depending on the incident light's wavelength and whether or not the hemoglobin is oxygenated or deoxygenated) at two different wavelengths. Ideally, the molar extinction coefficients of oxygenated and deoxygenated blood will differ substantially at each of the two wavelengths used. Traditionally, red and infrared light is transmitted through human tissue (e.g., ear or finger) and detected to determine oxygen saturation. LEDs are placed on one side of the tissue and a detector placed on the other side. Sampling of the transmitted light provides information about the ratio of oxygenated and deoxygenated hemoglobin in the blood. Such pulse oximeters, however, tend to be bulky and rigid and their use limited to certain tissue areas where sufficient light transmission in the red and IR wavelengths can occur.